In a field of cloud storage, a replication technique for avoiding a data loss caused by a disk fault or a block fault by replicating data is widespread. In recent years, an erasure code technique that further improves reliability and capacity efficiency by efficiently encoding data to provide minimum redundancy has been actively researched and developed.
However, RAID, a representative method of the erasure code technique, needs to calculate parities from all disks to be made redundant, posing a problem such that a data transfer amount between nodes increases in a distributed storage and a network is bottlenecked.
Accordingly, a technique that reduces a data transfer amount in a network when a single disk is recovered by calculating some of the parities from not all but some of the disks in a cloud storage is presented.
Note that techniques described in the following documents are known.
Japanese Laid-open Patent Publication No. 2005-44182
Japanese Laid-open Patent Publication No. 2007-257630
Japanese Laid-open Patent Publication No. 07-200187